The goal of this project is to develop safe and effective treatments against the damage to the brain caused by organophosphate (OP) induced status epilepticus (SE). Exposure to organophosphates has been identified as a major chemical threat for terrorist attacks against civilians or for exposure by an accident or natural disaster. Advances have been made to stop SE, but at present there are no therapies available to prevent the long term morbidity associated with SE. Our research laboratory has made a major advance in understanding how SE causes neuronal damage and the development of acquired epilepsy. We discovered that following OP SE there is a prolonged elevation in hippocampal neuronal calcium (Ca2+) that lasts for over a week. Furthermore, the Ca2+ plateau plays a major role in causing SE induced neuronal damage and the development of acquired epilepsy. We made a breakthrough in our preliminary research and discovered that hypothermia treatment following OP SE can prevent the Ca2+ plateau following SE. This study will develop this novel finding and test the Central Hypothesis that hypothermia applied after SE can rapidly reverse the long lasting Ca2+ plateau and thus decrease or prevent the SE induced neuronal loss and development of acquired epilepsy. This study will use the organophosphate, diisopropylfluorophosphate (DFP) to induce OP SE in rats. Our laboratory is ideally suited to conduct these studies and has developed the necessary skills to carry out the following specific aims: Aim 1: Determine whether hypothermia can prevent the development of the Ca2+ plateau after SE when administered after DFP SE. Hypothesis: The Ca2+ plateau from SE can be prevented or reversed by treatment after DFP SE with hypothermia. Aim 2: Determine whether hypothermia prevents neuronal loss and the development of AE when administered after DFP SE. Hypothesis: Hypothermia can decrease or prevent neuronal loss and AE from SE when administered after DFP SE. Hypothermia is widely used in hospitals and ambulances to treat cardiac arrest and anoxic brain injury. The preliminary results demonstrate the feasibility of these studies and underscore the potential significance of conducting this exploratory study. If these preliminary findings are documented, this study may provide the first insight for the use of hypothermia as an effective CounterACT measure to protect the brain against organophosphate toxicity.